1. Field of the Invention
The present invention relates to a device for securing at least one optical fibre to a optical apparatus.
2. Discussion of the Prior Art
There are known optical apparatus such as, for example, optical sensors operating with a single emission wavelength (colour), comprising a photo-emitter and a photo-detector (photo-elements). The photo-emitter generates a beam of light which is channelled into an optical fibre so that it is transported into a region to be monitored. The light reflected from the monitored region is channelled into another optical fibre and transported to the photo-detector.
In known optical sensors, each of the two optical fibres, that used for emission and that used for detection, is held in position, with respect to the photo-emitter and the photo-detector, by its own securing means of the screw, lever or button type.
Consequently, each securing means requires its own stage of manufacture, and each fibre requires its own alignment and fixing operation.
However, these known sensors do not enable the operator to check in a direct way the correct alignment of a fibre with a photo-element.
A first aspect of the present invention therefore consists of a device for securing at least one optical fibre to an optical apparatus, the said optical apparatus comprising at least one photo-element mounted on a supporting element and at least one optical fibre which can be connected to the said photo-element by means of the said securing device, characterized in that at least a part of the said securing device is made from a transparent material which makes a region of the coupling between the fibre and the photo-element visible.
According to a preferred embodiment, the said device comprises a cover made from transparent material. The said supporting element is also made from transparent material.
Preferably, the said transparent material is selected from the group comprising glass, polycarbonate (PC), polymethyl methacrylate (PMMA), polystyrene (PS), acrylonitrile-styrene (SAN), acrylonitrile-butadiene-styrene (ABS), polyphenylene oxide (PPO), polyurethane (PUR), polysulphone (PSU), polyamide (PA), polyvinyl chloride (PVC), and polyphenylene sulphide (PPS).
The known securing means are also particularly inadequate for multiple-fibre optical sensors comprising two or three photo-emitters, each capable of emitting a light beam of a predetermined colour and optically connected to a corresponding emission fibre. Typically, for example, three-fibre optical sensors may have red emission for the detection of white-green contrasts, and blue emission for the detection of white-yellow contrasts. Four-fibre sensors offer the function of colour reading and discrimination by means of blue, green and red emission. These optical sensors make different types of emission available to a user and, therefore, have the advantage of being adaptable to different applications.
A second aspect of the present invention therefore consists of a device for securing at least one optical fibre to an optical apparatus, the said optical apparatus comprising at least one photo-element, at least one optical fibre which can be connected to the said photo-element, and at least one supporting element provided with at least one guide hole for the said at least one optical fibre, characterized in that it comprises a slide provided with at least one slot, the said slide assuming a first and a second predetermined position, the said slot, in the said first position of the said slide, being coaxial with the said hole of the said supporting element and freely housing the said optical fibre, and the said slot, in the said second position of the said slide, being out of alignment with the said hole and exerting on the said optical fibre a force which keeps the optical fibre secured in the said hole.
According to a preferred embodiment, the said slide is provided with at least two slots. In particular, the said optical apparatus is provided with at least two optical fibres.
According to another preferred embodiment, the device comprises a cover provided with at least one hole for the passage of the said optical fibre, the said cover being provided with an enclosure capable of supporting the said slide so that it is free to slide, and of housing elastic means in engagement with the said slide to keep it in the said second position.
Preferably, the said slot comprises a semi-circular portion having a radius greater than that of the said optical fibre.
In particular, the said semi-circular portion of the said slot has a projecting arm.
The said slot is substantially C-shaped.
Additionally, the said semi-circular portion has a notch capable of imparting elasticity to the said arm.
According to a further preferred embodiment, the said slide is provided with a pin which is used for centring the said elastic means.
The said slide is advantageously made from transparent material. The said cover is also made from transparent material. The said supporting element is also made from transparent material.
Preferably, the said transparent material is selected from those mentioned previously.
In this way a simple and efficient device for securing one or more optical fibres to an optical apparatus is made.
Making the slide and the cover from transparent material provides many advantages.
It is possible to see the optical fibres and the holes of the supporting element through the cover and the slide during the assembly operations. This makes it possible to check the correctness of the coupling of a fibre to a predetermined photo-element (photo-emitter or photo-detector) and the positioning of each fibre with respect to its particular photo-element, which is known to be a very delicate operation. It is also possible to check, at the moment of insertion of the optical fibres into the holes of the supporting element, whether the holes are free or obstructed: and whether a fibre is damaged, by the tearing of a sheath for example.
Finally, the photo-elements are visible through a very wide angle. This enables the different photo-emitters to be clearly distinguished by the colours of the light beams emitted and also enables the photo-emitters to be distinguished with certainty from the photo-detectors. Moreover, it is possible to check, even from a distance, whether any of them are damaged.
The securing device according to the invention is very practical in terms of assembly, since the slide, by means of each slot, performs the double function of releasing and securing an optical fibre. This is achieved by simple movements of the slide between two predetermined positions. Moreover, a multiplicity of optical fibres of the optical apparatus can be released and secured simultaneously by operating the slide alone.
The degree of force, or compression, exerted by each slot on each optical fibre, is predetermined, to make it possible to fix the fibre without damaging it or adversely affecting its capacity for transmitting light.